🧠 Neural Control and Coordination

18.1 Neural System

• All animals have a neural system made of special cells called neurons 🧪
• Neurons can detect, receive, and transmit different stimuli (signals) ⚡
• Simple invertebrates (like Hydra 🪸) have a basic network of neurons
• Insects 🐜 have a better-organized system with a brain + ganglia (nerve clusters)
• Vertebrates 🐦 have the most developed neural systems

18.2 Human Neural System

Two Main Parts:

1. Central Neural System (CNS) 🧠💪:
   • Includes the brain + spinal cord
   • Does all information processing and control 🎮
2. Peripheral Neural System (PNS) 🌐:
   • Includes all nerves connected to the CNS
   • Has two types of nerve fibers:
     1. Afferent fibers ⬆️: Carry signals from body organs to CNS
     2. Efferent fibers ⬇️: Carry signals from CNS to body organs

PNS Subdivisions:

• Somatic Neural System 💃:
  • Sends signals from CNS to skeletal muscles (voluntary movement)
• Autonomic Neural System 🤖:
  • Sends signals from CNS to involuntary organs (heart, stomach) and smooth muscles
  • Split into:
    • Sympathetic 🚨 (fight-or-flight response)
    • Parasympathetic 😌 (rest-and-digest response)

18.3 Neuron: Building Block of Neural System

• Neuron = Structural + Functional unit 🔧
• 3 Main Parts:
  1. Cell Body:
     • Contains cytoplasm and cell organelles
     • Has special Nissl’s granules (granular bodies)
  2. Dendrites 🌿:
     • Short, branched fibers extending from cell body
     • Receive signals from other neurons
  3. Axon 🚀:
     • Long fiber transmitting signals away from cell body

⭐ NEET Super-Important Concepts ⭐

1. CNS vs PNS: Central (brain/spinal cord) vs Peripheral (all nerves) systems
2. Afferent vs Efferent: Afferent = body → CNS ⬆️, Efferent = CNS → body ⬇️
3. Autonomic Subdivisions: Sympathetic (🚨 emergency) vs Parasympathetic (😌 relaxation)
4. Neuron Structure: Cell body + Dendrites (input) + Axon (output)
5. Somatic vs Autonomic: Voluntary muscles vs Involuntary organs